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  <div id="layout-content"><div id="function.func-get-arg" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">func_get_arg</h1>
  <p class="verinfo">(PHP 4, PHP 5, PHP 7, PHP 8)</p><p class="refpurpose"><span class="refname">func_get_arg</span> &mdash; <span class="dc-title">返回参数列表的某一项</span></p>

 </div>
 
 <div class="refsect1 description" id="refsect1-function.func-get-arg-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>func_get_arg</strong></span>(<span class="methodparam"><span class="type">int</span> <code class="parameter">$position</code></span>): <span class="type"><a href="language.types.declarations.html#language.types.declarations.mixed" class="type mixed">mixed</a></span></div>

  <p class="para rdfs-comment">
   从用户自定义函数的参数列表中获取某个指定的参数。
  </p>
  <p class="para">
   该函数可以配合 <span class="function"><a href="function.func-get-args.html" class="function">func_get_args()</a></span> 和 <span class="function"><a href="function.func-num-args.html" class="function">func_num_args()</a></span>
   一起使用，从而使得用户自定义函数可以接受自定义个数的参数列表。
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-function.func-get-arg-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>
    
     <dt>
<code class="parameter">position</code></dt>

     <dd>

      <p class="para">
       参数的偏移量。函数的参数是从 0 开始计数的。
      </p>
     </dd>

    
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.func-get-arg-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   返回指定的参数，错误则返回 <strong><code>false</code></strong>。
  </p>
 </div>


 <div class="refsect1 errors" id="refsect1-function.func-get-arg-errors">
  <h3 class="title">错误／异常</h3>
  <p class="para">
   当在自定义函数的外面调用的该函数的时候会发出一个警告，
   或者是当 <code class="parameter">position</code> 比实际传入的参数的数目大的时候也会发出一个警告。
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-function.func-get-arg-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-5083">
    <p><strong>示例 #1 <span class="function"><strong>func_get_arg()</strong></span> 例子</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">()<br />{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$numargs&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">func_num_args</span><span style="color: #007700">();<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"Number&nbsp;of&nbsp;arguments:&nbsp;</span><span style="color: #0000BB">$numargs</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(</span><span style="color: #0000BB">$numargs&nbsp;</span><span style="color: #007700">&gt;=&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"Second&nbsp;argument&nbsp;is:&nbsp;"&nbsp;</span><span style="color: #007700">.&nbsp;</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">)&nbsp;.&nbsp;</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br />}<br /><br /></span><span style="color: #0000BB">foo</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">3</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents"><p>以上例程会输出：</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
Number of arguments: 3
Second argument is: 2
</pre></div>
    </div>
   </div>
  </p>

  <p class="para">
   <div class="example" id="example-5084">
    <p><strong>示例 #2 byRef 和 byVal 参数的 <span class="function"><strong>func_get_arg()</strong></span> 示例</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">byVal</span><span style="color: #007700">(</span><span style="color: #0000BB">$arg</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'As&nbsp;passed&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">)),&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$arg&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'baz'</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'After&nbsp;change&nbsp;&nbsp;:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">)),&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />}<br /><br />function&nbsp;</span><span style="color: #0000BB">byRef</span><span style="color: #007700">(&amp;</span><span style="color: #0000BB">$arg</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'As&nbsp;passed&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">)),&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$arg&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'baz'</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'After&nbsp;change&nbsp;&nbsp;:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">)),&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">$arg&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'bar'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">byVal</span><span style="color: #007700">(</span><span style="color: #0000BB">$arg</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">byRef</span><span style="color: #007700">(</span><span style="color: #0000BB">$arg</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents"><p>以上例程会输出：</p></div>
    <div class="example-contents screen"><br />
As passed     : &#039;bar&#039;<br />
After change  : &#039;baz&#039;<br />
As passed     : &#039;bar&#039;<br />
After change  : &#039;baz&#039;<br />
    </div>
   </div>
  </p>

 </div>


 <div class="refsect1 notes" id="refsect1-function.func-get-arg-notes">
  <h3 class="title">注释</h3>
  <blockquote class="note"><p><strong class="note">注意</strong>: <p class="para">As of PHP 8.0.0, the func_*() family of
functions is intended to be mostly transparent with regard to named arguments,
by treating the arguments as if they were all passed positionally,
and missing arguments are replaced with their defaults.
This function ignores the collection of unknown named variadic arguments.
Unknown named arguments which are collected can only be accessed through the variadic parameter.</p></p></blockquote>
  <blockquote class="note"><p><strong class="note">注意</strong>: <p class="para">如果参数以引用方式传递，函数对该参数的任何改变将在函数返回后保留。As of PHP 7
the current values will also be returned if the arguments are passed by value.</p></p></blockquote>
  <blockquote class="note"><p><strong class="note">注意</strong>: 
   <span class="simpara">
    此函数仅返回传递参数的副本，不会考虑默认（未传递）参数。
   </span>
  </p></blockquote>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.func-get-arg-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><a href="functions.arguments.html#functions.variable-arg-list" class="link"><code class="literal">...</code> 语法</a></li>
    <li class="member"><span class="function"><a href="function.func-get-args.html" class="function">func_get_args()</a></span></li>
    <li class="member"><span class="function"><a href="function.func-num-args.html" class="function">func_num_args()</a></span></li>
   </ul>
  </p>
 </div>


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